In a pretensioner recited in Japanese Patent Application Laid-Open (JP-A) No. 2008-285136, a position fixing piece in the form of a folded plate anchors movement of a piston. When the position fixing piece is crushed and the piston is moved, a gear member is turned and a restraining force on an occupant from a webbing is increased.
In this pretensioner, it is preferable if an action of the position fixing piece that is caused by movement of the piston is effectively made consistent, particularly if the position fixing piece is formed in a rod shape.